The present invention relates generally to a method and apparatus for fabricating a molded workpiece and, more particularly, to a method and apparatus for fabricating a molded workpiece wherein at least one electro-optical sensor is employed for sensing when molding material has substantially filled an inner cavity of a mold.
High Speed Resin Transfer Molding (HSRTM) is a process which has been employed in the past for manufacturing workpieces such as structural automotive components. The HSRTM process is a reactive polymer processing method in which a liquid resin mixture is injected into a heated mold, cured, and removed from the mold. The filling of the mold with the resin mixture is an important step in the HSRTM process. If the mold is not properly filled with the resin mixture, the molded part may have air pockets or voids formed therein. If, on the other hand, an excess amount of resin material is injected into the mold, which material leaves the mold through vent lines associated with the mold, a costly waste of material results. Unfortunately, an adequate control for overcoming these disadvantages associated with the mold filling step has not yet been provided for in the prior art.
Accordingly, a highly reliable, fast response, "fill-state" sensor suitable for use in a manufacturing environment is needed to implement real-time control of a molding material injection process to ensure that the inner cavity of a mold is properly filled with molding material and that a costly waste of molding material does not occur.